Thermostatic control for electric ovens and the like



y E. 1.. FONSECA THERMOSTATIC CONTROL FOR ELECTRIC OVENS AND THE LIKEFiled Sept. 11 1924 2 Sheets-Sheet l INVENTOR BY'M V ATTORNEYS Mai 10'I927.

y E. 1.. FONSECA THERMOSTATIC CONTROL FOR ELECTRIC OVENS AND THE LIKE 2Sheets-Sheet 2 Filed Sept. 11 1924 INVENTOR Z M w llcq HM/U W ATTORNEYSPatented May '10, 1927.,

UNITED STATES PATENT OFFICE.

EDWARD L. -FONSECA, OF NEWARK, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGN-MENTS, TO THE WILCOLATOR COMPANY, OF NEWARK, NEW JERSEY, A CORPORA- TIONOF DELAWARE.

THEBMOSTATIC CONTROL FOR ELECTRIC OVENS AND THE LIKE.

Application filed September 11, 1924. Serial No. 737,049.

My invention relates to a thermostatic con trol for electric ovens, andhas to do particularly with a three point switch which is controlled bythermostatic means so that one circuit may be closed when the oven isbelow the desired temperature and a second circuit may be closed whenthe desired oven temperature is reached. These circuits may include anywell known form of apparatus intended to control the main circuit whichsupplies the electricity to the heating elements of the oven but suchapparatus and the particular manner in which it is connected form nopart of my present invention. In the accompanying drawings which showillustrative examples of devices embodying my invention Fig. .1 shows aplan .view of one form of such device with the cover-plate removed; Fig.2 is a longitudinal section of l the device shown-in Fig. 1; Fig. 3 is asection on line 3-3 of Fig. 2; Fig. 4 is a perspective view showing away in which the device may be mounted on the stove; Fig. 5

is a longitudinal sectional view of a modified form of device with aportion of the oven well illustrated; Fig. 6 is a fragmentary end viewof the device shown in Fig. 5, but without the oven wall, and Fig. 7 isa plan view of this form of device with a portion of the cover platebroken away.

Referring particularly to Figs. 1, 2 and 3, 10 is a base plate which hasone end bent out at 11, where an opening 12 is provided for the cablecontaining the connecting wires as illustrated in connection with theform of device shown in Fig. 7. Attached to the base plate 10 are twobrackets 13 and 14. These brackets must be insulated from the base plateand from each other, and I find this can be done quite cheaply byproviding openings 15 considerably larger in diameter than the attachingbolts 16, and by covering both faces of this portion of the base plate10 with mica strips 17 in which areopenings just large enough to receivebolts 16. The mica strips 17 are held in place by rivets 18. Pivotallymounted in bracket '13 is an arm 19 which carries a double fa cedcontact 20. A spring .21 exerts pressure to'force the arm 19 towardsbase plate 10. In the same way bracket 14 carries an arm 22, which hasposition shown in Fig. 2. A third contact 26- is carried by a plate 27,which is attached to base 10. Three wires 28,29 and 30 are connected tobrackets 13 and 14 and plate 27 respectively.

When the parts thus far described are in the positions shown in Fig. 2in which one face of contact is in engagement with contact 26, and theother face is-spaced from the'contact 23, the wires 28 andare connectedand the wires 28 and 29 are disconnected. If arm 19 is moved to carryits free end away from plate 10, the circuit connection from Wire 28 towire 30 will be broken and on further movement of the arm 19, contact 20will engage contact 23 and thus elec trically connect wires 28 and 29.

In order to move arm 19 I supply a push "rod 31 which slides in abearing 32 attached tobase 10. The outer end of rod 31 contacts with arm19 While the inner end con tacts w th thermostatic element 33. In the"example shown this element/is of the type made of two strips ofmaterials having different temperature coefiicients, the composite stripbeing adapted to bend under the influence of heat and this is the formof thermostat which I prefer to use. However other forms of thermostaticelements may be used and still retain many of the advantages of myinvention.

The thermostatic element 33 is rather loosely mounted at one end and atthe other end is pivotally connected 1 with the threaded sleeve 35; Thesleeve 35 moves on thescrew 36 which rotates in a bearing 37 and has onits outer end a small gear 38. A dial 39 carriesa gear 40 which mesheswith the gear 38. The dial 39 may carry any appropriate temperaturemarks or cooking instructions, as illustrated in con nection with theform of device shown in Fig. 5. A'spring 41 is providedto keep the dialunder tension so that it will stay where placed.

When connecting the device I intend that the parts shall be in theposition shown in on the bracket 34,.

Fig. 2 when the oven is heating upthat is,

out until'contact moves away from con- I tact 26 and, on furthermovement against through an opening in contact 23. This engagement ofcontacts 20 and 23 efi'ects the closure of a circuit which causes theheat to be turned off from the oven. The exact temperature at which thiswill take place can readily be controlled and adjusted by rotating dial39.

The ordinary temperature range at which an oven is used is from 250 F.to 550 F., and this may be the range of temperatures controllable bydial 39, so that when the oven is not in use and cools down to roomtemperature a considerable movement of ele-.

ment 33 will take place. However by the arrangement which I provide thiswill place no load on the element 33 for it will simply move away fromrod 31. Provision is also made totake care of another possible source ofstrain. Let us suppose that a very hot oven has been used so that sleeve35 has been forced out to the limit of movement of dial 39, but element33 has bent enough to move contact 20 away from contact 26. Suppose theoperator now wishes to use theoven at a much lower tem eraturvnd sorotates dial 39 to draw bach sleeve'35. This exerts additional pressureon rod 31, but no harm results as arms 19 and 22 can both swing outagainst only the relatively light pressure exerted by sprin 21 and 24:.

The temperature range ldetween the time that contact 20 leaves contact26 and the time that it meets contact 23which is substantially thefluctuationran e of the oven for any given settin of dia 39,can becontrolled by adjusting the position of contact 23.

In Figs. 5, 6 and 7 a modified form of device is shown. The two formsare similar in principal and accordingly corresponding parts arev givenlike reference characters but with a prime added, and where thefunctions are identical the parts are not again described in detail. Inthis modified form it will be noted that push rod 3l'-is pivotallyconnected to the thermostatic element 33 and that instead of having abearing corresponding to bearing)32, it passes freely ase 10. In orderto hold rod 31 in place its outer end is re duced in size and thisreduced portionslides in an appropriate 0 ning in arm 19.

The upper end 0 element 33' is riveted to a su port 35 which pivots on abracket 34. T 's bracket likewise carries a threaded bearing 37 for theshaft 36' on the outer "endof which the dial 39 mounted. The

inner end of shaft 36 is adapted to bear against support 35 so that asdial 39 is rotated the lower end of element 33' can be forced towardsbase 10'.

In these views I likewise show the coverlate 42, and also the stop 43carried by ial 39' which co-operates with indicator point 44 tolimitrotation of dial 39.

Figs. 4 and 5 show the way my device is installed on an oven. A portionofthe outer wall 45 of theoven 46 is cut away so that the thermostaticelement will be inside of the oven with base 10 against wall 45. Thispermits the thermostatic element to function properly, and at. the sametime leaves the dial 39 readily accessible.

It is to be understood that the examples given are intended only asillustrations of we s in which my invention may be utilized an that manymodifications may be made without departing from'the spirit of myinvention.

What I claim is:

1. In a thermostatic control mechanism, the combination of a fixedcontact, a movable contact spaced therefrom, a movable arm carrying acontact which lies between said spaced contacts, a thermostatic elementpivotally mounted to swing, this element aving a portion which ismovable to different positions as the element is exposed to differenttemperatures, means engaging the element to limit its swinging movement,means for adjusting the position of the limiting means, and a connectionbetween the said movable portion of the element and the said arm.-

2. In a thermostatic control mechanism, the combination of a pair ofcontacts in spaced relation, an arm carrying a contact lying between thecontacts, this arm being adapted to swing to bring its contact into engaement with one or the other of the contacts rst mentioned, athermostatic element pivotally mounted to swing and having a portionmovable to different positions in accordance with temperaturevariations, adjustable means for limiting the swinging movement of theelement, and a connection between the movable rtion of the element andthe contact-carrying arm for transmitting the movement of the elementdue to temperature variations to the arm.

3. In a thermostatic control mechanism, the combination of a pair ofcontacts disposed in spaced relation, a swinging arm carrying a contactlying between the two spaced contacts, this arm being arranged to swingto brin its contact into enga ement with either 0 the said contacts, a termostatic element mounted to swing, this element having a portionmovable to difierent positions in accordance with temperaturevariations, a rod connecting the movable portion of the element and theswinging arm and arranged to transmit the movement of the movableportion of the element resulting from temperature variations to the arm,and manually operable means for swinging the element on its ivot toalter the effect of movements of t e movable portion of the element uponthe movable arm.

4. In a thermostatic control mechanism, the combination of a stationarycontact, a movable arm carrying a contact spaced from the contact firstmentioned, a second movable arm carrying a contact adapted to be broughtinto engagement with one or the other of the contacts first mentioned, athermostatic element mounted to swing about a pivot, an operativeconnection between the second arm such that the arm is moved inaccordance with the movement of the elc' ment due to temperaturechanges, and manually operable means for swinging the element on itspivot to vary the effectiveness of the connection.

5. In a thermostatic control mechanism,

' the combination of a stationary contact, a

movable'arm carrying a contact adapted to engage the stationary contact,a thermostatic element mounted to swing about a pivot, a rod adapted totransmit the movement of the element to the arm, and manually operablemeans for adjusting the element with reference to its pivot to vary theaction of the element upon said rod.

6. In a thermostatic control mechanism, the combination of a stationarycontact, a movable arm carrying a contact held normally in definitespaced relation to the contact first mentioned, a movable arm having acontact 1 ing between the stationary contact and t e contact on thefirst movable arm, this arm being arranged to permit its contact toengage with one or the other of the said contacts, and the two armsbeing arranged to swing in unison with their contacts engaged, athermostatic element mounted to swing about a point, a rod connectingthe element with the second movable arm, and manually operable means formoving the element with reference to its (pivotal point to vary itsaction upon the r0 means for transmitting the movement of the elementdue to temperature changes to the arm, and manually o erable means forvarying the position of t 1e thermostat with reference to its pivotalpoint to vary its effect upon said transmitting means.

8. In a thermostatic control mechanism, the combination of a stationarycontact, a movable arm, a contact on the arm adapted to be brought intoengagement with the stationary contact, a thermostatic element adaptedto swing about a pivotal point and having a portion movable to differentpositions in accordance with temperature changes, a rod adapted totransmit the movement of the movable portion of the element due totemperature changes to the arm, and manually o erable means for adjusting the position 0 the thermostatic element with reference to itspivotal point.

9.' In a thermostatic control mechanism,

the combination of a stationary contact, a

movable arm carrying a contact adapted to engage the stationary contact,a thermostatic element having one end pivotally mounted, this elementhaving a portion movable to different positions as the element isexposed to temperature variations, a manually ad'usta'ble device forvarying the position 0 the element with reference to its pivotal point,and a rod engaging the part of the element movable in accordance withtemperature variations and transmitting such movements to the arm.

EDWARD L. FONSECA.

